Donald S. Schauwecker

Prospective Study of Fluorodeoxyglucose–Positron Emission Tomography Imaging of Lymph Node Basins in Melanoma Patients Undergoing Sentinel Node Biopsy

PURPOSE To prospectively compare positron emission tomography (PET) imaging of regional lymph node basins to sentinel node biopsy (SNB) in patients with American Joint Committee on Cancer (AJCC) stage I, II, and III melanoma localized to the skin. METHODS Patients with cutaneous melanoma with Breslows depth greater than 1 mm (AJCC T2-4N0M0) or localized regional cutaneous recurrence (TxN2bM0) underwent whole-body imaging of glucose metabolism with fluorodeoxyglucose (FDG) PET followed by SNB. PET scans were interpreted in a blinded fashion and compared with histologic analyses of SNB specimens and clinical follow-up examination. Nodal tumor volumes were estimated. RESULTS Eighty-nine lymph node basins were evaluated by FDG-PET and SNB in 70 assessable patients. Eighteen patients (25.7%) had lymph node metastases at the time of FDG-PET imaging: 17 proved by SNB (24.3%) and one by follow-up examination (1.4%). Median tumor volume in positive sentinel node basins was 4.3 mm3 (range, 0.07 to 523 mm3). Sensitivity of SNB for detection of occult regional lymph node metastases was 94.4%, specificity was 100%, positive predictive value (PPV) was 100%, and negative predictive value (NPV) was 98.6%. Sensitivity of FDG-PET was 16.7%, specificity was 95.8%, PPV was 50%, and NPV was 81.9%. At a median follow-up duration of 16.6 months, seven patients (10%) developed recurrent disease. PET predicted one recurrence (14.3%) in a node basin missed by SNB. CONCLUSION FDG-PET is an insensitive indicator of occult regional lymph node metastases in patients with melanoma because of the minute tumor volumes in this population. FDG-PET does not have a primary role for staging regional nodes in patients with clinically localized melanoma.

Inefficacy of F‐18 fluorodeoxy‐D‐glucose‐positron emission tomography scans for initial evaluation in early‐stage cutaneous melanoma

The purpose of the current study was to determine the sensitivity and specificity of initial F‐18 fluorodeoxy‐D‐glucose‐positron emission tomography (FDG‐PET) scanning for detection of occult lymph node and distant metastases in patients with early‐stage cutaneous melanoma.

Initial assessment of positron emission tomography for detection of nonpalpable regional lymphatic metastases in melanoma.

The purpose of this pilot study is to determine the feasibility of position emission tomography with fluorodeoxyglucose (FDG‐PET) for detection of nonpalpable regional lymph node metastases in patients with melanoma.

Symptom-limited arm exercise increases detection of ischemia during dipyridamole tomographic thallium stress testing in patients with coronary artery disease.

Exercise combined with dipyridamole during thallium stress testing in patients with coronary artery disease (CAD) increases the frequency of angina and ischemic ST changes in the electrocardiogram. Evidence for an increase in thallium abnormalities has been inconclusive. We prospectively examined 54 consecutive patients who underwent coronary angiography and tomographic thallium with dipyridamole (0.57 mg/kg) alone and combined with symptom-limited dynamic arm exercise. Most patients presented with a history of chest pain and 49 had angiographic evidence of significant coronary stenosis (50% diameter narrowing). Thallium abnormalities were scored blindly by consensus. The number of abnormal segments (total and ischemic) and indexes of left ventricular dysfunction, such as increased lung uptake or ischemic dilation, were compared in the 49 patients with CAD. During arm exercise more patients had evidence of ischemia (39 vs 30; p < 0.001), and the number of ischemic segments increased significantly from 1.3 +/- 1.5 to 2.5 +/- 2.2 (p < 0.001). There was also a significant increase in the indexes of left ventricular dysfunction, ischemic dilation (10 vs 4 patients; p < 0.03) and increased lung uptake (16 vs 5 patients; p < 0.001). Patients who exercised had increased thallium evidence of extent and severity of ischemia and more frequent indexes of left ventricular dysfunction. Thus, symptom-limited arm exercise improves detection of extent and severity of ischemia in patients with CAD undergoing dipyridamole thallium stress testing.

Comparison of technetium-99m sulfur colloid and in vitro labeled technetium-99m RBCs in the detection of gastrointestinal bleeding

Twenty-seven paired Tc-99m sulfur colloid (SC) and Tc- 99m RBC studies were evaluated for the detection of Gl bleeding. The only two positive Tc-99m SC studies had positive early Tc-99m RBC studies as well. There were 15 other positive Tc-99m RBC studies (three during the first hour) and these were associated with normal Tc- 99m SC scans. Approximately 70% of the positive Tc- 99m RBC studies occurred after 1 hour. Tc-99m RBCs should be the initial test in patients with Gl bleeding.

The value of SPECT-thallium scanning in screening for myocardial contusion

In this prospective study of 40 patients sustaining blunt chest trauma, the value of single-photon-emission computed tomography (SPECT)-thallium scanning in the prediction of morbidity due to cardiac contusion was examined. Twelve patients developed cardiac complications—arrhythmias, ventricular conduction defects, and pericarditis. The sensitivity of SPECT-thallium scans was 55.6%, and the specificity was 32.1%, with an accuracy of 37.8%. Accuracy of the initial electrocardiogram (ECG) was 85%, with a sensitivity of 91.7% and a specificity of 82.1%. Patients with a normal ECG on admission rarely developed cardiac complications. It is concluded that SPECT-thallium is no a useful screening tool in this patient population.

Tc-99m HMPAO brain survival study reveals flow to the cerebrum but none to the cerebellum.

One of the advantages of the Tc-99 m HMPAO brain survival study is that it visualizes flow to the cerebellum. Several cases have documented flow to the cerebellum but none to the cerebrum. This appears to be the first case of flow to the cerebrum but none to the cerebellum. The patient was admitted in hypertensive crisis (376/250). CT revealed a bleed into the cerebellum. A Tc-99 m HMPAO brain survival scan obtained the same day revealed no flow to the cerebellum but flow to the cerebrum. A repeat Tc-99 m HMPAO brain survival scan obtained the next day revealed no flow to either the cerebrum or the cerebellum

Nuclear medicine evaluation of focal fatty infiltration of the liver.

Focal fatty infiltration of the liver (FFIL) occasionally may be mistaken as metastatic disease, primary liver malignancy, or other space-occupying lesions on CT or ultrasound studies, especially if there is significant mass effect. In these confusing cases, Xe-133 liver imaging has been advocated for confirmation of FFIL, since such studies have been reported to be sensitive and specific. The authors present results of four Xe-133 and four Tc-99m sulfur colloid scans in six patients with FFIL. Xe-133 imaging was found useful for diagnostic confirmation in only one patient and was misleading in the other three. Routine liver-spleen imaging was a more reliable method of confirmation, since no focal defects were found in any of the patients.

Indeterminate lung imaging. Can the number be reduced

During a 2½-year period, 1131 patients with suspected pulmonary embolism had ventilation-perfusion lung scans; 150 of these patients also underwent pulmonary angiography. In a retrospective study, these 150 patients were re-evaluated using the reference criteria of Biello and Alderson, with 62% read as indeterminate. Twenty patients who had chronic obstructive pulmonary disease with retention of Xe-133 in greater than 50% of the lung fields without corresponding radiographic abnormality were included. Ventilation/perfusion matches and mismatches could be correctly determined in 15 of these patients. These 15 of 20 studies could be correctly reclassified as low-probability, while the other five remained indeterminate. With increasing intervals between ventilation/perfusion lung imaging and the onset of symptoms, the percentage of patients with proven pulmonary emboli correctly diagnosed as high probability continuously decreased, and the percentage of studies read as indeterminate constantly increased. Serial chest radiographs suggested that the development of infiltrates in the region of the embolus convert high-probability ventilation/perfusion scans to indeterminate.

In-111 granulocyte response to intervening surgery. Evidence of sustained in vivo viability

A patient with chronic osteomyelitis had surgery performed between the early and delayed images of an ln-111 granulocyte scan. The early images showed no uptake, while the delayed images demonstrated marked soft tissue uptake, which was felt to be secondary to the inflammation of the intervening surgery. It was concluded that granulocytes, when labeled with ln-111, remain viable and can respond to inflammation that occurs after their injection.